Insulator.



GHARLE$ LIE G. FORTESGUE, OF EITTSBURGH,

JEIGUSE ELECTRIC AND MANUFACTURING Mil /KEANE,

YLVAHEA.

Specification oi Letters Patent,

PENNSYLVANIA, ASSIGNOR T0 WESTING- A CQRPO'BATION 0F PENN- INSUIJATOR.

Patented Mar. 1%, 1918.

Application filed May 11, 1914., serial No. 837,?4-2.

To all whom it may concern:

Be it known that 1, CHARLES Ln G. Fonrnsoun, a subject of the King ofGreat Britain, and a resident of Pittsbur 'h', in the county ofAllegheny and State of ennsylvania, have invented a new and usefulImprovement in Insulators, of which the following is a specification.

My invention relates to electrical insulating bodies or structures, andparticularly to such structures as are employed for supportinghigh-voltage lines or conductors. I

I have discovered that, if the electrostatic flow lines in fieldsexternal to insulating bodies are precluded from concentrating upontheir surfaces, the insulating structures are capable of effectivelyinsulating coni highly desirable to obtain equal divisions of sign.

ductors of extremely high potentials. In order to provide insulatingstructures of the most efiicient design, it is necessary to con siderthe application of the insulating materials, and also the production ofsubstantially uniform electrostatic fields in the regions external tothe structures. Accordingly, the E maximum insulating strength ofstructures .may be obtained if the external electrostatic fields are sodistributed as to create uniform surface stresses upon the 1nsulat1ngstructures.

A desirable form qfa transmission line insulating support comprises asystem of con-' densers connected in series relation. It is potential.difierence between the insulating units comprlslng the condensers, butthis 1s not the only req'iurement of a successful de- The aforementionedcondition may actually be obtained, andyet the system of insulators willbreak down at a very much lower potential difference than the sum of thebreakdown strengths of each insulator. To increase the strength of thesystem, the external electrostatic field should be so distributed as tosecure a substantially uniform surface distribution of the electrostaticstresses imposed thereupon, as above mentioned. The external field willthen be substantially uniform and vision of potential between theindividual insulators or condensers. The eificiency of the combinationis thereby increased in exactly the same way'that the efficiency of acondenser-type bushing of a particular design is increased by theaddition of a large dish, namely, because it completes the surfacedlsagree with the ditributio-n of the electrostatic field in the regionsurrounding the bushing. lit is unnecessary, however, to 'so design anlnsulating support as to efiect an equal di- VlSlOIl of the potentialdifference between the various units comprising the support in order toobtain good results, inasmuch as a substantially uniform distribution ofthe electrostatic field surrounding the support greatly enhances theinsulating value of the support. Of course, when itis preferred to havethe most efficient design and to minimize the overall length of thestructure, it is desirable, for maximum efficiency, that the externalfield be substantially unlform and agree with the division of potentialbetween the individual insulators comprising the structure. a v

One object of my invention is to provide an insulating structure forelectrical conductors that 'shall be simple in construction,

and that shall substantially preclude the con-.

ing description and the accompanying draw-.

ing in which Figures 1 and 2 are sectional and side elevational views,respectively, of insulating supports equipped wlth devices built inaccordance with my invention, and

Figs. 3 and 42 are similar views of suspension type insulators embodyingforms of my invention.

Tn Fig. 1, a high-potential conductor 1 is secured, by means of aclamping device 2, to an insulating support 3 which engages a pin 3 Thesupport 3 comprises a series of insulators or condensers 4 superposedupon one another, the upper and lower members 5 and (5 of which areprovided with discoidal shaped electrodes or conducting members 7 and 7that extend laterally beyond the insulators 4:.

Each insulator 4 comprises a metal bell or petticoat 8 into which ismolded an insulating compound 9. A recess 10 is provided in order thatthe adjacent bell may benested therein, substantially as shown. Thesurface 11 of the dielectric or insulating compound 9 which isintercepted between two adjacent bells, is so molded as to conform tothe lines of force of the electric field between the two adjacent bells.For the most economical design, it is desirable to have each insulator 1take up approximately an equal share of the difference of potentialbetween the conductor 1 and the structure from which the conductor-is tobe insulated.

In order to obtain the highest efficiency, the discoidalshapedelectrodes 7 and 7" are supplied to ap oximate, the result which wouldbe obtained by bounding the insulating supportS by twoinfinite parallelconducting planes perpendicular to the axis of the insulator. By meansof the electrodes or conducting members 7 and 7, the electrosta-ticfield external to, and surrounding, the

insulating structure 3, will be substantially uniform. The condition forequal division of otential between the units 4 of the insulatingstructure is that the flux leaving each electrode or metal hell 8 shallbe of the same quantity; this means that the capacity of' each electrode8 to ground must be inversely as-its potential, and that the capacitybetween adjacent pairs of electrodes 8 must be equal. This isapproximated very closely if the high potential electrode 5 and theAgain, if the dimensions of the insulating structure as shown, aredoubled, the capacity of the insulating structure to resist .hi hpotentials is doubled.

t is apparent, however, that, by the ap- 7 plication of discoidal shapedbOdIQS 7 andto types of insulating supports other than i the one shownin Fig. 1, as, for example,

the'support shown in Fig. 2, the insulatmg.

strength of the support is greatly enhanced.

' The conductor 1 in Fig. 2 is supported by any adequate means upon theinsulating structure 12 which comprises a plurality of superposedporcelain insulators 13 of a well known, type. The 'discoidal hhapedbodies .7 and 7 a are supplied to the upper andlower portions of the suport"12 in order to efiect a substantially uni orm distribution of theelectrostatic field surrounding the. support 12 and to thereby precludeconcentration of electrostatic stresses upon the surfaces thereof. v

In Figs 3 and 4, I have shown my invent1on applied to suspension typeinsulators.

shown.- The lower ends of the rods 17 are proyided with hooks 19 whichengage eyelets 20 formed in the top portions of. an ad acent conducting.member 16. To securely hold the rods17 in pl ace, the insulatingcompound or dielectric 9 is molded around the top portio 18 of the rods,and the exposed surface 11 is preferably molded to conform to theelectrostatic flow lines between the adjacent conducting members 16. Inorder to disengage the hook 19 from a coijperating eyelet 20, it isdesirableto provide a recess 21 in'the molded material. v The recess 21will not affect the insulating properties of the structure.

In this instance, a high potential conductor 22 is suspended from aclamping device 23 disposed on the lower end of a rod 24 secured to alower conducting member 25. The conducting member or electrode 25, incooperation with an upper conducting member or electrode 26, is providedwith laterally extending portions 27 and 28, respectively. The whole issuspended from a hook 29 attached to any suitable supporting tower,pole, etc. (not shown). The electrodes 25 and 26 serve in this structurefor the same purpose that the electrodes 7 and 7'- served' in thestructures shown in Fi 1 and 2, and, what is said relative to t e mosteflicient design of the structure in 1, may be applied with equaleffectiveness to the most eflicient design of a structure to be made inaccordance with the device shown in Fig. 3.

In Fi 4, the insulators 14 have been replaced y porcelain suspensiontype insulators 30.of a well known type of construction. While thedevice'shown in Fig. 4 is not as efiicient in resisting potentialstresses as the device shown in Fig. 3, it has, how- Although I-haveshown and described devices of specific structural details, many 1modifications may be effected therein within the spirit and scope of myinvention, and I desire that only such limitations shall be imposed asare indicated in the appended claims.

I claim as my invention:

The combination withan insulator compr sing a plurality of superposedseparate umts, of conducting members secured to the upper and lowerportions thereof, said members havmg' laterally extending flux-dis- 1tributing isurfaces that coincide with the -to preclude substantiallythe concentration of electrostatic stresses upon. the surfaces of loweredges ofthe upper and: lower units of said insulator in order'to producea substantially uniform surface distribution of.

the electrostatic stresses imposed thereupon.

2. The combination with an insulator comprising a plurality ofsuperposed separate units, of parallelly disposed conductingmemberslaterally extending beyond the insulator and secured to the upperand lower portions thereof, the laterally extending surfaces of saidconducting members lying in the same planes as the lower edges of theupper and lower units in order to efiect a substantially uniformdistribution of the electrostatic field surrounding the insulator.

3. The combination with an insulator com prising a plurality ofsuperposed and separate insulating units, of parallelly disposed andlaterally extending discoidal shaped electrodes for the upper and lowerportions of the insulator, the flux-distributing surfaces of saiddiscoidal shaped electrodes lying in the same planes as the lower edgesof the upperand lower insulating units in order the insulator.

4. The combination with an insulating structure comprising a series ofsuperposed insulating members, of conducting extensions for the upperand lower members that extend laterally beyond said members and lie inthe plane's coinciding with therlower edges of said members in order toeffect a uniform surface distribution of the electro; static field inthe region surrounding the said insulating structure.

5. An insulating support for an electrical conductor comprising abuilt-up column of insulating members, and laterally-extendingelectrodes for the upper and lower members thereof, said electrodesbeing of relatively wide extent in order to produce a substantiallyuniform distribution of the external electrostatic field wherein itagrees with the division of potential between the insulating memberscomprising said built-up column.

6. An insulating support comprising. a plurality of separate unitsarranged one above the other -and constituting a system of condensersconnected in series relation, and means to effect a substantiallyuniform distribution of the external electrostatic field surrounding thesuperposed units.

7. An insulating support for an electrical conductor. comprising aplurality of separate and similar units arranged above one another andconstituting a system of condensers connected in series relation, andmeans to effect asubstantially uniform distribution of the externalelectrostatic field surrounding the said superposed units in order toobtain a substantially equal division of the potential differencestherebetween.

8. An insulating support for an electrical conductor comprising aplurality of separate unis arranged above one another and constitutmg asystem of condensers havlng sub.

stantially equal capacities, and means to effect a substantially uniformdistribution of the external electrostatic field surrounding the saidcondensers in order to obtain a substantially equal division of thepotential differences therebetween.

9. An insulating support for an electrical .sulating units, anddiscoidalshaped electrodes extending laterally from the top of the upperinsulating unit and from the bottom of the lowest insulating unit inorder to provide an external electrostatic field that agrees with thedivision of potential between the said insulating units.

11. An insulator comprising a built-up structure of equallyspacedandidentical insulating units, and conducting members extendinglaterally from the top of the upper insulating unit and from the bottomof the lowest insulating unit, said conducting members severally havingfiat parallel surfaces that are opposed to each other in order toprovide an external electrostatic field that agrees with the division ofpotential between the said insulating units.

12. An insulating support comprising a series of superposed insulatingunits, and fiat conducting members extending laterally from the top ofthe upper unit and from the bottom of the lowest unit in order toinclose all-of said units in asubstantially- Eniformly distributedexternal electrostatic eld. 'In testimony whereof, I have hereuntosubscribed my name this 29th day of April,

, CHAR-LES LE G. FORTESCUE.

Witnesses:

LENORE FLANAGAN,

B. B. HINES.

- conductor comprising a plurality of separate

